The invention relates to a method for producing an electrical connection between a flexible circuit board with single-sided access and a metallic contact partner, to an arrangement of the elements referred to with an electrical connecting point realized between them and to a module for complete installation in an engine or a gearbox of a motor vehicle, which uses such an electrical connecting point.
It is already known to use laser welding methods for realizing an electrically conducting connection between a flexible circuit board and a metallic conductor. Benefits in principle of this technology are that no additional parts, such as rivets for example, are required for creating the connection and that the connections can be fabricated at low cost in production and with great variability in design.
However, for practical applications it is disadvantageous that laser welds can currently only be carried out on circuit boards with access from both sides. In addition, further measures are often required in addition to irradiation with laser light to ensure that a dependable and mechanically stable connection is created. For instance, U.S. Pat. No. 5,676,865 describes a laser welding method in which openings lying opposite one another are first introduced into the insulating layers of the flexible circuit board on the bottom and top sides, so that a conductor strip running in between is exposed on both sides in the regions of the openings. The exposed conductor strip is then provided with a central hole of reduced diameter. The rim of the hole in the conductor strip is subjected to a forming operation, so that it comes into contact with an electrical conductor on which the flexible circuit board is resting with one side. The welding of the conductor strip to the conductor takes place in the formed region of the rim of the hole by means of a laser.
In the case of this method, it is problematical that, on account of the central hole, occasionally there is not adequate conductor strip material available for a dependable and durable welded connection.
To remedy this, German Patent Application DE 199 06 807, which is not a prior publication, proposes a method which makes it possible without mechanical working (for example hole punching or forming operations) of the conductor strip to produce a welded connection between the latter and a contact partner. However, even in the case of this method there must be access to the conductor strip from both sides. A disadvantage of this is that circuit boards with access from both sides are much more expensive than circuit boards of comparable size and type with access from one side. The reason for this is that circuit boards with access from one side can be produced from continuous material in a low-cost process known as a reel-to-reel process, while circuit boards with access from both sides have to be produced from individual sections of material (on account of the high requirements for the alignment accuracy with respect to the access openings lying opposite one another).